In wireless communication systems generally, a downlink (DL) resource is allocated to user terminals for receiving ACK/NACK signaling from the base station. In the Long Term Evolution (LTE) of the Third Generation Partnership Project (3GPP) Universal Mobile Telecommunications System (UMTS) wireless communication protocol, for example, it has been proposed to assign a PHICH to a MU-MIMO terminal in a non-adaptive HARQ state using a resource block (RB) that implicitly points to the assigned PHICH, wherein multiple MU-MIMO terminals are multiplexed on a common time frequency resource. It has also been proposed to assign a PHICH resource to multi-user MU-MIMO terminals from an assigned PHICH group using a 3-bit Cyclic Shift Index (CSI) to avoid ambiguous PHICH assignments between terminals multiplexed on the same time frequency resource. The 3-bit Cyclic Shift Index (CSI) is being considered for inclusion on the scheduling grant primarily for setting a cyclic shift the terminal uses for its demodulation of reference signal (RS) transmissions, especially for MU-MIMO transmissions. The cyclic shift setting guarantees orthogonality between MU-MIMO terminals multiplexed on the same uplink time frequency resource.
The various aspects, features and advantages of the disclosure will become more fully apparent to those having ordinary skill in the art upon a careful consideration of the following Detailed Description thereof with the accompanying drawings described below. The drawings may have been simplified for clarity and are not necessarily drawn to scale.